Radioimmunotherapy (RIT) is a promising therapy for cancer, wherein radionuclides are linked to monoclonal antibodies specific for antigens expressed solely on tumor cells. Once the mAb locates the tumor cell, the radionuclide decays and kills the cell. The compounds that have so far undergone clinical trials are based on beta-emitting radionuclides, because they can be reliably linked to the mAb. However, alpha radiation has significant advantages for distributed carcinomas, including short path length and much greater cytotoxicity The development of alpha-emitting radionuclides has been severely hampered by a lack of robust chelates for radionuclides with therapeutically desirable half- lives. This project aims to develop a new encapsulate with 100% containment, suitable for all actinide radionuclides. PROPOSED COMMERCIAL APPLICATIONS: This encapsulate will enable alpha particle RIT methods to be developed for the treatment of leukemias, lymphomas, micrometastates, lung cancer, and other cancers where tumors are smaller than a few cell diameters. The development of such a therapy has a potential market of approximately 300,000 Americans/yr.